This invention relates to high pressure combustors for generating a mixture of steam and combustion gas downhole in an oil well. The mixture is injected into the surrounding oil reservoir to displace heavy oil from the reservoir.
The energy consumption in this process is great. It takes the energy equivalent of one barrel of oil to displace three barrels of oil from the reservoir. There is an incentive to burn the cheapest fuel available, which is usually the heavy crude oil produced from the same reservoir. Heavy oils will not light off and burn without substantial heat. It is simpler to heat air rather than oil, because the weight of air is 14-15 times the weight of oil. Also, heavy oil is not suitable for use in a catalytic heat exchanger, which is part of the present invention, because heavy oil would foul the surface of the heat exchanger. This invention discloses a means for providing heated air for burning heavy oil in the later stages of a multi-stage combustor.